Towers Road, in the Horsetooth Mtn trail system, is a well-established Fort Collins time-trial route - mainly for mountain bikers, but also for trail runners.

http://www.discoverytrail.org/

This popular, hilly 11-mile loop is near Estes Park, CO.  There is a Strava segment for the loop.

http://www.rockymountainhikingtrails.com/lumpy-ridge-loop.htm

https://www.nps.gov/romo/planyourvisit/old_fall_river_road.htm

Opened in 1920, Old Fall River Road earned the distinction of being the first auto route in Rocky Mountain National Park offering access to the park's high country. In the minds of many park visitors, the relatively subtle old route remains foremost. Unlike Trail Ridge Road, which is well known for being the highest continuous paved road in the nation, the Old Fall River Road is a much more "motor nature trail."